It's a good idea to have 1 main site location. Whether it is http://www.seocactus.com/ or http://seocactus.com/, when launching your site you should choose one and stick to it. You don't want the search engines thinking you have duplicate content.
Something like this should work.
Welcome to our new site SEOCactus.com. Here at SEO Cactus you will find some tools, tips, and tricks to better improve your website(s) within the worlds of Search Engine Optimization and Search Engine Marketing.
Be sure to contact us with any questions you may have.